Method of manufacturing cylinder lines

ABSTRACT

A ROUGH SURFACED SAND CAST SLEEVE OF CYLINDER IRON WITH A GENERALLY CYLINDRICAL INTERIOR PERIPHERY AND AN AXIALLY RIBBED EXTERNAL PERIPHERY HAS THE SURFACES OF ITS EXTERNAL RIBS GROUND TO TRUE CYLINDRICAL FORM, PREFERABLY IN A CENTERLESS GRINDER, TO PROVIDE AN ACCURATELY PREDETERMINED OVER-ALL FORM AND DIMENSION. THE RESULTING EXTERNAL CYLINDRICAL SURFACES ARE CHUCKED AND THE CENTRAL OPENINGS BORED IN TRUE CONCENTRICITY THEREWITH FOR UNIFORM WALL THICKNESS, THE CHANNELS BETWEEN THE RIBS BEING LEFT WITH ROUGH SAND CAST SURFACES SO THAT A CYLINDER CASTING WILL ANCHOR ITSELF MECHANICALLY TO THE LINER WITHOUT VOIDS OR AIR POCKETS.

M. o. HOLTAN ETAL 3,561,104

METHOD OF MANUFACTURING CYLINDER LINES Feb. 9, 197'! Original Filed Jan. 10, 1966 mvsmon 0 z! Mn ale/cs a flazmw 14 44 Ian J H04. rAm/ M, M /@w MW ATTORNEYS United States Patent Office 3,561,104 METHOD OF MANUFACTURING CYLINDER LINES Maurice O. Holtan and William J. Holtan, Wauwatosa, Wis., assignors to Slinger Foundry Company, Inc., Sliuger, Wis., a corporation of Wisconsin Original application Jan. 10, 1966, Ser. No. 519,782, now Patent No. 3,439,586, dated Apr. 22, 1969. Divided and this application Dec. 9, 1968, Ser. No. 800,017 Int. Cl. B23p 17/00 US. Cl. 29--527.6 6 Claims ABSTRACT OF THE DISCLOSURE This application is a division of application'Ser. No. 519,782, filed Jan. 10, 1966, and now Pat. No. 3,439,586.

Ideally, cylinder liners or sleeves should be cast iron which is at least 90% pearlitic with less than free ferrite and having predominantly type A graphite with uniform flake size in random distribution for wear and lubricating qualities. They should be of uniform Brinell test and Within a specified range of hardness, without hard spots or chilled edges, for uniform machineability.

There are, generally speaking, two types of liners: the one kind that is inserted into a cylinder block and the other kind that is cast into a cylinder block. This invention relates to the kind of liner that is cast into a cylinder block, crankcase, compressor housing, etc., and which is composed of a different metal than the liner, usually an aluminum alloy. This type of liner should have its periphery provided with roughness or irregularities of some sort to which the aluminum alloy, when poured or injected around it, can anchor itself mechanically to obtain the best bond possible without voids or air pockets. A smooth exterior surface is not desirable as it allows the aluminum to slide rather than roll and fuse, such as occurs When the liner has a rough surface. The rolling action of the molten metal in'contact with a liners rough surface prevents air pockets and voids between the aluminum cylinder and the liner, thereby eliminating hot spots or thermal insulating areas in the product resulting from the bonding of the two metals.

The instant invention contemplates liners or sleeves cast vertically with circumferentially spaced external vertical ribs. Static cast sand molds are preferred. They leave the surface rough. When the exterior surfaces of the ribs are ground to true cylindrical conformation, the intervening channels retain their rough finish. This roughness, plus the shoulders at the sides of the ribs, provides excellent bonding surfaces between the iron and the aluminum resulting in good cylinder casting anchorage. A centerless grinder is preferably used for machining the outside diameter to provide uniformity of dimension. The operation is extremely rapid because a relatively small area has to be machined and because the intervening channels provide immediate clearance for removed material.

The accurately cylindrical chuck-engaging surfaces are now fixed in an appropriate chuck of any type and the Patented Feb. 9, 1971 central opening is bored to provide a piston bearing surface in true concentricity with the cylindrically ground exterior surfaces. The resulting sleeve will have a uniform wall thickness for even dissipation of heat in all areas of the liner for efiicient operation of the resulting engine, air compressor, etc. When the sleeve is cast in a cylinder, a precision product of uniformly high quality results.

In the drawings:

FIG. 1 is a diagrammatic cross section through a sand mold and a pair of sleeves being cast therein in accordance with this invention.

FIG. 2 is an enlarged fragmentary detail view in perspective showing a portion of the sleeve as cast.

FIG. 3 is an enlarged fragmentary detail 'view in perspective showing a portion of the cast sleeve after peripheral surfaces of the ribs have been cylindrically ground.

FIG. 4 is a View in perspective showing a sleeve which has been completed by the precision machining of its inner periphery concentrically with the external cylindrically ground surfaces to produce walls of uniform thickness.

FIG. 5 is a fragmentary diagrammatic plan view showing a modified embodiment in which the ribs are more Widely spaced than in FIGS. 1 to 4.

The sand mold 6 includes, by way of example, cope 8, drag 10, cores 12 (in most cases this is not a core, but green sand within and part of the mold) and gates, runner, riser and down sprue, collectively identified by reference character 14 and shown in a schematic manner. The castings 16 represent the first step in the production of cylinder liners in accordance herewith. Each is as shown in FIG. 2, except that sometimes a casting may have an integral flange as shown at 17 in FIG. 1.

The inner surface 18 of each casting will have the roughness characteristic of a sand casting. This is represented by stippling. Similar roughness of surface appears on the outside of each casting, as shown on the ribs 20 and the intervening channels 22.

The rough-surfaced casting 16 is now machined externally to cylindrical conformation, the machining preferably being done in a centerless grinder and limited to the external periphery surfaces 24 of ribs 20 as indicated by the shading of surfaces 24 in FIG. 3. If the flanged tube is used, a special grinding wheel is required. The bottoms 26 and sides 28 of channels 22 remain with the rough sand-cast finish as shown by stippling. The objective is to produce a cylindrical surface which can be grasped by a precision chuck. In effect, it is only necessary to remove those rough spots which project beyond the desired surface.

The casting is now grasped by any conventional precision chuck and held for machining of its interior to produce a smooth bore which will be within permissible tolerances of sleeve wall thickness. It will be understood that normally the central opening is machined by boring. Reference to chucking, machining, grinding and boring is intended to be generic to express the precision with which the inner surface is rendered cylindrical and concentric with the outer surfaces of a sufficient number, or all, of the ribs to permit accurate positioning and concentricity of finishing.

As shown diagrammatically in FIG. 5, the ribs 200 may be relatively of much smaller over-all area and much greater spacing in relation to the intervening channels 220 than has been shown in FIGS. 1-4.

The liner is now complete. The cost of the important centerless grinding is low because removal of metal is confined to the narrow surfaces at the outsides of the ribs. The immediate escape of waste via the channels 22 also contributes both to speedand accuracy. The resulting accuracy is such that there are practically no rejects. The bond to the cylinder casting is excellent be cause of the ribs and because of the sand cast rough surfaces in the channels. Moreover, the fact that the ribs are axial precludes short circuiting between circumferentially adjacent ports cut through the cylinder.

Because of the design of the sleeve and method of casting, this invention with proper foundry practice, can meet metallurgical requirements, both chemical and physical, for wear resistance and long life. The invention ensures concentricity of the outside and the inside machined surfaces with resulting uniformity of wall thickness within commercial tolerances for even dissipation of heat from the liner to the adjacent metal, and the liner after being machined, retains the described rough exterior surfaces necessary to diffuse the metal cast around it, thereby eliminating air pockets and voids, as well as obtaining a resulting excellent mechanical bond between the two metals.

We claim:

1. A method of cylinder liner manufacture which comprises the steps of statically casting an iron tube with interior of generally cylindrical rough-surfaced form and exterior having rough-surfaced ribs and grooves, machining the exterior rough surfaces of ribs to true cylindrical smooth form, grasping such exterior surfaces, and concurrently machining the interior of the tube in concentricity with said exterior surfaces.

2. A method according to claim 1 in which the machining of the rough rib surfaces is a centerless grinding operation, the grooves remaining rough surfaced.

3. A method according to claim 2 in which the machining of the interior is a boring operation.

4. A method of cylinder liner manufacture which comprises the step of casting a sleeve provided exteriorly with alternating ribs and grooves and with rough surfaces throughout, the step of machining the exterior rough surfaces of the ribs to true cylindrical smooth form, leaving the surfaces of the grooves rough and the step of machining the interior of the sleeve in true concentricity with the smooth exterior machined surfaces of the ribs.

5. A method according to claim 4 in which the sleeve is initially sand cast of cylinder iron to provide the rough surfaces aforesaid, and in which the ribs are formed to extend generally axially.

6. A method according to claim 5 in which the machined true cylindrical smooth exterior surfaces of the ribs are grasped to hold the sleeve in position while the interior periphery of the sleeve is machined in concentricity with the said exterior surfaces of the ribs.

References Cited UNITED STATES PATENTS 1,480,571 1/1924 Selker 308-237 2,099,126 11/1937 Larsen.

2,134,749 11/1938 Burt 29527.6X 2,833,099 5/1958 Horst 29527.6 3,130,481 4/1964 Ahlen 29527.6X 3,165,983 1/1965 Thomas 123--l93X JOHN F. CAMPBELL, Primary Examiner D. C. REILEY, Asssitant Examiner US. Cl. X.R. 164-76 

